Ok, I just installed my Sapphire Pulse RX580 - but I do not get the boot screen, except for just a second or 2 right at the end, and it shows up as an R9 XXX. Is there more than one iteration of the Sapphire Pulse RX580? Mine has 2 HDMI, 2 DP and 1 DVI. Pics attached.

You will not get the boot screen with an RX580, and the R9..... description is normal in Sierra.
I believe in High Sierra it lists correctly, as its the card in Apple's eGpu.
This is the same card I have in my mac.

OOTB meaning no setup, no drivers required..... unfortunately no boot screen
But, really is it required?
One thing I recently discovered, is to upgrade to HS, you need an Apple EFI card to perform a firmware update.
Luckily I still have my old card.

Yep, as someone else has pointed out, you would need High Sierra to have the correct name shown.
Indeed the drivers in High Sierra will likely be more up to date and probably perform better than the RX580 driver in Sierra.

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